The vast majority of binary packages in the AMD64 release were built
from exactly the same sources as the packages for the other
architectures. There were a small number of exceptions, however. To
make life easier for distributors of AMD64 discs, the extra sources
needed for those packages have been added to the last binary disc in
each AMD64 set (i.e. CD#13 and DVD#2). Source requirements can
therefore be met easily for AMD64.

I looked into jigdo files,
and according to http://amd64.debian.net/docs/package_changes.txt
IMHO there are more additional sources than needed.
Really different sources, but "orig.tar.gz" are the same:
NgBQZ4DJnsYgmk9IjC61BQ=Debian:pool/main/b/base-config/base-config_2.53.10-0.0.0.1.pure64.tar.gz
94f_X8dm3UM78z_RmxHoHQ=Debian:pool/main/c/choose-mirror/choose-mirror_1.11-0.0.0.1.pure64.tar.gz
8IWt8CfVbNGngpfjQYosfg=Debian:pool/main/libt/libtool1.4/libtool1.4_1.4.3-21.0.0.1.pure64.tar.gz
877wQ-ItYI1vBTLnDb1-Yg=Debian:pool/main/l/linux86/linux86_0.16.14-1.2.0.1.pure64.diff.gz
q-a8A883cDp_OZG-yLX3FQ=Debian:pool/main/l/linux86/linux86_0.16.14.orig.tar.gz
B_lyIVOsBxXJBs6HPdWBdA=Debian:pool/main/s/syslinux/syslinux_2.11-0.1.0.1.pure64.diff.gz
pzxLMmKcklZ2ZgxGjvPPGg=Debian:pool/main/s/syslinux/syslinux_2.11.orig.tar.gz
Only rebuild of package, therefore sources already in "official sources":
HYveJD5wJLHMfhN-ZymIHg=Debian:pool/main/g/gnupg/gnupg_1.4.1-1.dsc
zBGzSbZivzgQRw4KUu9UXg=Debian:pool/main/g/gnupg/gnupg_1.4.1-1.diff.gz
HMd8aUO6qnESIulUu9eF5Q=Debian:pool/main/g/gnupg/gnupg_1.4.1.orig.tar.gz
Sources for udeb - in amd64 are built from "released sarge" version,
in other architectures from some older version.
Therefore again sources already in "official sources".
0B8q77NrlqPE1LTBEmpbew=Debian:pool/main/g/glibc/glibc_2.3.2.ds1-22.dsc
OzXUkQZxbTWLtWCdX8_K9A=Debian:pool/main/g/glibc/glibc_2.3.2.ds1-22.diff.gz
uYK_atfryGItO4HVHES3ig=Debian:pool/main/g/glibc/glibc_2.3.2.ds1.orig.tar.gz
8ssekjEmDKDWoA498-d9Yg=Debian:pool/main/h/hdparm/hdparm_6.1-2.diff.gz
uIOUS8JqSA3Myug3xN33Mg=Debian:pool/main/h/hdparm/hdparm_6.1.orig.tar.gz
mxQ58Q_Naxf1f82JVp7gbg=Debian:pool/main/u/util-linux/util-linux_2.12p-4.diff.gz
1H6CD2iAwhyLTAx-inN2zA=Debian:pool/main/u/util-linux/util-linux_2.12p.orig.tar.gz
On the other hand, it may be usefull to copy ia32-libs
from DVD source-3 to DVD amd64-2.
After that, only 4 DVD carry all what is needed for amd64.
Similarly, it may be usefull to copy ia32-libs
from DVD source-3 to DVD ia64-3.
After that, DVD source-3 might be dropped entirelly.
I hope, that such shuffle might be possible in August for 3.1r1.
Again, thank you very much for amd64.
Petr